UW Researchers Link Habitat and Nutrition with Wyoming’s Moose Population

February 28, 2014 — A preliminary University of Wyoming report of moose habitat
in five regions of the state and one in northern Colorado shows habitat is
linked to nutrition condition, reproduction and calf survival in moose.

“The Statewide Moose Habitat Project is about linking
climate and habitat condition to nutritional condition, reproduction and calf
survival in moose,” says Brett Jesmer, a UW master’s student in zoology and
physiology, and lead writer of the report. “Results from this study are aimed
at understanding the recent declines in moose calf production in the region,
and to provide managers with tools with which they can monitor proximity to
carrying capacity (the maximum number of animals a habitat can support) in
their respective herds.”

The preliminary report looked at autumn nutrition of moose
and winter habitat condition. Habitat condition and the demands associated with
gestation, lactation and calf-rearing combine to determine autumn nutritional
conditions, which determine pregnancy in female moose. The report was submitted
to the Wyoming Game and Fish Department in January, and will eventually provide
the agency with early-warning metrics to predict where and when moose declines
are likely to occur.

Other contributors to the preliminary annual report are
Jacob Goheen, a UW assistant professor of zoology and physiology; Matt
Kauffman, associate professor and leader of the Wyoming Cooperative Fish and
Wildlife Research Unit; Kevin Monteith, assistant researcher and professor of
zoology and physiology; and Aly Courtemanch, a regional wildlife biologist for the
Wyoming Game and Fish Department.

A numbers game

Jesmer’s report indicates that trying to define ideal
numbers of moose in various areas of Wyoming is an elusive task.

“The ideal number of moose is not the same for any one area,
or for any period of time due to variation in environmental conditions,” says
Jesmer, who has been studying the issue, which is the subject of his master’s
thesis, since fall 2011. “What that creates is a moving target of what an ideal
population size should be.”

Currently, moose reproduction and calf survival throughout
Wyoming is a mixed bag. In some areas Jesmer studied, recent moose calf
production is increasing slightly (Jackson and Uinta, and North Park, Colo.) or
remaining stable (Big Horn and Sublette).

On average, over the past three years, approximately 1,200
moose have been counted in the Sublette County moose herd, according to the
Wyoming Game and Fish Department.

“This constitutes what we believe is the largest moose
population in the state and in the Rockies,” Jesmer says.

In other areas, such as the Snowy Range, moose calf
production appears to be declining. Up until recently, Jesmer says indications
were that this moose population was growing rapidly because the mammal had been
introduced fairly recently, during the mid-1980s, in a habitat that had not
been intensively browsed. But numbers may now be approaching the maximum that
habitat can support (carrying capacity), and this would result in decreased
calf production and survival, Jesmer says.

Potential reasons for declines in calf production and
factors that may impact the carrying capacity of female moose include: current
and historic over-browsing of certain habitat; shifts in forage quality due to
climate warming and drying; and disturbances, such as intense wildfires and
bark beetle outbreak. In addition, predators in the northwest corner of Wyoming
may impact calf survival; and an emerging disease, known as carotid artery
worm, can cause moose to be in poor nutritional condition, go blind, have
malformed antlers, cropped ears and noses, and even die.

To better understand these population patterns, the report’s
objectives include:

-- Establishing ways to measure habitat condition that can
be readily used by wildlife managers.

-- Exploring alternative early-warning metrics related to
nutrition and behavior to head off declines in calf production.

Moose scat offers
clues

To assess the winter diet and pregnancy rates of moose, the
research group collected fresh scat samples of adult moose only. To help them
locate scat, the group used specially trained detection dogs from a Missoula,
Mont., organization called Working Dogs for Conservation.

When fresh scat was identified in the field, researchers
logged the approximate location, and habitat information was collected. Using
molecular techniques in the lab, scat piles were assigned to a particular individual.
The sex of the animals was determined before diet and pregnancy analyses.

The same protocols were used to characterize the range of
foraging behavior and the forage quality (willow habitat and all other upland
habitat types) used by moose during the summer. In this study, the sex of the
animals was determined before diet and forage quality analyses.

In a process similar to that used by criminal forensic
scientists, the moose DNA is duplicated multiple times, Jesmer says. Nine
specific portions of the genome are “fingerprinted,” which allows researchers
to identify from which individual the moose scat came from and the sex of the
animal, Jesmer says.

“We can measure progesterone in the feces. That tells us if
they are pregnant,” he says.

Hunters provide a
helping hand

The research group also received assistance from hunters, who
salvaged the kidneys of moose that Jesmer and others studied for fat content
levels. Unlike humans, a lot of fat around a moose kidney is a key indicator
the animal is in good nutritional condition.

The nutritional condition of cows in the fall, the mating
season, determines whether they will get pregnant, Jesmer says.

“A female moose won’t get pregnant unless she has a minimum
6 percent body fat,” he explains. “The act of caring for a calf involves
lactation (from the mother), and the cost of lactation will drive down the fat
percentage of an animal.”

However, such assessments can be tricky. A cow could be in
poor condition (i.e., have little fat) come fall because she was successful at
birthing calves in the spring. On the flip side, a cow may possess healthy
amounts of fat around her kidneys for the mere reason she didn’t give birth
that spring.

“The cost of reproduction in females makes it difficult to
link kidney conditions back to the habitat,” Jesmer says. “So, we use male
kidneys. They don’t have those costs of reproduction, and the amount of fat
they can accumulate represents the condition of the habitat well.”

The research group looked at 346 moose kidneys for
nutritional conditional assessment during 2011-12 and another 190 in 2013.

More work to do

The research will continue this spring. The group plans to
complete genetic analyses of 1,022 fecal samples and obtain finalized diet
composition, diet quality, pregnancy and spring nutritional data sets. The goal
is to complete the research by fall 2014 and create a final annual report.

“A future component is to assess exactly what moose eat,”
Jesmer says. “We know willow is important. We have evidence they eat other
things, but we’re not sure how important other diet items are.”

When all of the data is compiled, comprehensive reports will
be produced for state and federal agencies, and presentations and materials
will be provided to the general public. Results are expected to be published in
peer-reviewed scientific journals this fall and early 2015, Jesmer says.

Photo:Brett Jesmer, a UW master’s student in
zoology and physiology, poses with a captured moose in the Hoback Basin of the Bridger-Teton
National Forest. Jesmer is studying the relationship between habitat and
nutrition on population numbers of Wyoming moose. (Brendan Oates Photo)